the Elasticity of Wires. 



419 



the wire is placed on the top of the screw F and adjusted to 

 the centre of the hole. The surface of the lower screw where 

 it grips the wire is filed to a V-notch ; this increases the hold 

 and allows of alignment. 



Fiff. 2. 



In all cases a considerable number of svving-swangs were 

 recorded, the number varying from 70 to 700 according to 

 the period, and the mean taken. 



For convenience, the four periods determined will be 

 referred to as the two horizontal periods and the two vertical 

 periods. 



The following table contains the results obtained for each 

 wire, the diameter given in every case is the mean of 10 mea- 

 surements ; the length is measured between the centres of the 

 grips. _ 



It will be noticed that in no case was a value of Poisson's 

 ratio found greater than 0'4 61 ; this, in view of the fact thai 

 Mr. Searle obtained several values above 0'5, is of interest 

 as illustrating a possible effect of the increase in diameter of 

 the wires used. 



In conclusion the author wishes to thank Professor Ewing 

 both for advice and the use of the different materials provided. 

 The above experiments were carried out in the Engineering 

 Laboratory at Cambridge. 



